CN111665411B - Modularized multifunctional MMC topology universal experimental platform and method thereof - Google Patents

Abstract

The invention discloses a modularized multifunctional MMC topology universal experimental platform and a method thereof, and belongs to the technical field of power electronics. The experimental platform is composed of modular hardware. The bridge arm module can be converted into a shaping circuit and a conducting switch circuit; the power module comprises an auxiliary power module and an alternating current-direct current side power port, can be connected with alternating current and direct current sources, and can be connected with a plurality of universal experiment platforms to meet the requirements of multi-terminal cooperative control experiments; the control module comprises a master controller and a slave controller. The platform can meet the requirements of MMC, HMMC, AAMC, HCMC, modularized multi-level DC-DC converters and other various topology experiments, and achieves the purpose of carrying out various topology experiments by using one platform. The modularized multifunctional MMC topology general experimental platform provided by the invention has the advantages of simplicity in operation, multiple functions, strong universality, strong expansibility, high safety and the like, and is beneficial to accelerating the conversion of scientific research results.

Description

Modularized multifunctional MMC topology universal experimental platform and method thereof

Technical Field

The invention belongs to the technical field of power electronics, and particularly relates to a modularized multifunctional MMC topology universal experimental platform and a method thereof.

Background

High-voltage direct current (HVDC) power transmission has the advantages of high power transmission efficiency, large capacity, variable trend of power flow, easy incorporation of a distributed power supply, fewer large-scale energy storage devices and the like, and gradually becomes a preferable scheme for long-distance, cross-region and large-capacity power transmission. The modularized multi-level converter (Modular Multilevel Converter, MMC) gradually becomes one of the converters with the most development prospect in the HVDC system by virtue of the characteristics of high modularization degree, good output waveform quality, low device switching frequency and the like. Because the full-bridge MMC has high cost, and the half-bridge MMC has no direct current fault ride-through capability, on one hand, in order to have certain direct current fault ride-through capability, an HMMC topology is provided; on the other hand, in order to save the cost, two kinds of hybrid converters of HCMC and AAMC are proposed in combination with the structural characteristics of the traditional two-level converter and MMC. However, HMMC, HCMC and AAMC have many urgent problems to be solved, such as high harmonic content at the dc side and difficulty in balancing capacitor voltage, and only MMC is currently put into use in HVDC engineering in a small amount. With the intensive study of the high-voltage direct-current power transmission system, the novel high-voltage direct-current power distribution system is paid attention to gradually, and due to the advantages of high voltage level, modularized design, multi-level output and the like of the MMC, a learner puts forward the topology of the modularized multi-level DC-DC converter, and the field gradually becomes a big research hot spot of the high-voltage direct-current power distribution system in recent years.

In order to further deeply study the characteristics, advantages and disadvantages and applicable conditions of MMC topologies and promote the application of the MMC topologies in actual engineering, a principle verification prototype is hoped to be built, simulation results are verified, and experimental results of different MMC topologies under the same conditions are compared. However, the construction of the principle verification prototype has a plurality of difficulties: the converter has huge structure, numerous modules and difficult circuit design, so that the hardware design difficulty is high; the control structure is complex, the signal types are various, the total data amount is huge, and the software design difficulty is high. The difficulty in constructing the principle verification prototype is high, and the period is long. At present, some existing principle verification prototypes have single structure function, poor expansibility and insufficient flexibility, and an experimental platform can only develop a topology experiment. Therefore, how to build a multifunctional MMC topology universal experimental platform, to realize that various MMC topologies can develop relevant verification experiments on one universal experimental platform, accelerate the conversion of scientific research achievements, and become an unsolved problem in the field of HVDC engineering.

Disclosure of Invention

In view of the above, the invention combines the common characteristics of MMC topologies, and utilizes the thought of modular design to provide a modular multifunctional MMC topology universal experiment platform and a method thereof, wherein the universal experiment platform can perform experiments related to MMC, HMMC, AAMC, HCMC and a modular multilevel DC-DC converter, a plurality of universal experiment platforms can also realize multiport cooperative control experiments, the topology switching is convenient and rapid, and the expansibility is strong.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the modular multifunctional MMC topology general experimental platform consists of a cabinet and modular hardware installed in the cabinet, wherein the modular hardware comprises a bridge arm module, a sampling module, a power module, a control module, an inductance module, an isolation transformer and a protection module;

the bridge arm module comprises an upper bridge arm module and a lower bridge arm module, and the input end of each phase of upper bridge arm module is connected with the positive electrode of a direct current side power port of the power module after being subjected to direct current side protection of the converter level current sampling and protecting module of the sampling module; the input end of the lower bridge arm module is connected with the negative electrode of the direct-current side power port of the power module; the output ends of the upper bridge arm module and the lower bridge arm module are connected with the input end of the inductance module after being sampled by the converter level of the sampling module; two output ends of each phase in the inductance module are connected, and are connected with the input end of the isolation transformer after being sampled by the converter level of the sampling module and being protected by the alternating current side of the protection module; the output end of the isolation transformer is connected with an alternating current side power port of the power module;

the sampling module is provided with a plurality of voltage detection ports and a plurality of current detection ports, the voltage detection ports are arranged in parallel at the positions of the upper bridge arm module, the lower bridge arm module, the input end and the output end of the isolation transformer and the direct current side power supply port of the power supply module, and the current detection ports are arranged at the bridge arm side, the alternating current side and the direct current side of the converter; the working states of the bridge arm module, the sampling module, the power module, the inductance module, the isolation transformer and the protection module are controlled by the control module.

Preferably, the control module comprises a master controller and slave controllers, wherein the master controller is provided with a plurality of optical fiber communication interfaces, and the optical fiber communication interfaces are communicated with the slave controllers through optical fibers; the slave controller is integrated with a high performance DSP.

Preferably, a bridge arm module state display screen and a voltage and current display screen are arranged in the cabinet, the bridge arm module state display screen is connected with the main controller through a network cable, and displayable bridge arm module states comprise a normal state, an operating state, an overvoltage state, an overcurrent state, an overtemperature state and a communication error; the voltage and current display screen is connected with the power module and the sampling module.

Preferably, the sampling module is divided into a converter stage sampling and a full-bridge sub-module sampling, and the converter stage sampling includes converter stage voltage and current sampling. The converter level sampling is an independent unit with complete functions and consists of a sampling plate and a slave controller. The full-bridge submodule sampling is composed of a miniaturized sampling plate and a slave controller, and can collect capacitance voltage of the full-bridge submodule and current flowing through the full-bridge submodule.

Preferably, the protection module comprises a direct current side protection, an alternating current side protection and a full bridge sub-module protection, wherein the direct current side protection and the alternating current side protection comprise an air switch and a controllable circuit breaker which are connected in series.

Preferably, the bridge arm module is formed by connecting a plurality of full-bridge sub-modules in series, and each full-bridge sub-module is an independent unit formed by full-bridge sub-module sampling of the sampling module, full-bridge sub-module protection of the slave controller, the power board and the protection module.

Preferably, after the full-bridge sub-module in the bridge arm module is controlled by the control module, the full-bridge sub-module can be converted into a switching circuit and a shaping circuit formed by a full-bridge structure or a half-bridge structure.

Preferably, the power module comprises an auxiliary power module, an alternating current side power port and a direct current side power port.

Preferably, the inductance module is composed of 6 groups of inductance submodules with adjustable inductance values.

The invention also aims to provide an experimental method of the modular multifunctional MMC topology universal experimental platform, which comprises the following steps:

step 1: determining topology types and the number of full-bridge submodules required by a shaping circuit and a switching-on circuit according to experimental requirements, and controlling redundant full-bridge submodules to be in a cut-off state if the required number is smaller than the number provided by a general experimental platform; if the number is equal to the number provided by the universal experiment platform, no adjustment is needed; if the number is larger than the number provided by the universal experiment platform, a plurality of additional full-bridge submodules are added in series;

step 2: the control module of the test platform is internally integrated with a modularized program, which comprises MMC, HMMC, AAMC, HCMH and a control and debugging program of the modularized multi-level DC-DC converter, and corresponding connection modes, control and modulation programs are selected according to topology types:

scheme 1: MMC experiment

Selecting MMC control and debugging programs, controlling Quan Qiaozi modules to be shaping circuits, and operating in a full-bridge structure or half-bridge structure state;

scheme 2: HMMC experiment

Selecting HMMC control and debugging programs, controlling Quan Qiaozi modules to be shaping circuits, and controlling full-bridge submodules to be in a full-bridge structure or half-bridge structure state according to the number of required full-bridge structures and half-bridge structures;

scheme 3: AAMC experiment

Selecting an AAMC control and debugging program, and controlling the full-bridge submodule to be in a state of conducting a switch circuit, a full-bridge structure or a half-bridge structure according to AAMC topology;

scheme 4: HCMC experiment

Selecting an HCMC control and debugging program, connecting the conducting switch circuits in series, connecting the shaping circuits in series, connecting the conducting switch circuits of the upper bridge arm module and the lower bridge arm module with the input ports of the shaping circuits, and connecting the output ports of the shaping circuits with the input ends of the inductance modules; then, according to the quantity of the required on-switch circuits and the full-bridge structures, the full-bridge submodules are controlled to be in a state of the on-switch circuits or the full-bridge structures;

scheme 5: modular multilevel DC-DC converter experiment

Selecting a control and debugging program of a modularized multi-level DC-DC converter, wherein for the modularized multi-level DC-DC converter with single-ended output, a main circuit only selects a pair of upper bridge arm modules and lower bridge arm modules, an output resonance circuit consists of an inductance module and another bridge arm module, and an output port of a bridge arm where the main circuit is positioned is connected with an output port of the other bridge arm module through the inductance module; the upper bridge arm module and the lower bridge arm module of the main circuit control the full-bridge submodule to be in a full-bridge structure or half-bridge structure state according to the number of required full-bridge structures or half-bridge structures, the bridge arm module of the output resonant circuit is used as an adjustable capacitor, the overall capacitance value of the bridge arm module is adjusted by controlling the switching number of the full-bridge submodule, and charging is not needed during operation;

step 3: and starting the power module, executing corresponding control and debugging programs through the main controller, acquiring experimental data and storing the experimental data.

Based on the technical scheme, compared with the prior art, the invention has the following advantages:

(1) The multifunctional MMC topology universal experimental platform provided by the invention adopts the serial full-bridge submodules to form 6 bridge arms, and the bridge arms are converted into the shaping circuit formed by the full-bridge structure or the half-bridge structure or are converted into the on-switch circuit by controlling, so that the corresponding connection mode and control and modulation algorithm can be selected according to different topology types by matching with the modularized design inductance module, the relative experiments of the MMC topology such as MMC, HMMC, AAMC, HCMC and modularized multi-level DC-DC converter can be satisfied, the purpose of the modularized universal design of multiple functions of one universal experimental platform is realized, and the multifunctional MMC topology universal experimental platform has the advantages of convenience in switching different MMC topologies, high safety and reliability, high flexibility, strong expansibility and the like, and is beneficial to accelerating the conversion of scientific research results.

(2) The universal experiment platform provided by the invention is provided with the ports reserved on the alternating current side and the direct current side respectively, so that the universal experiment platform can be connected with alternating current and direct current sources, can be connected with various experiment platforms, and is convenient for carrying out multi-terminal cooperative control related experiments.

(3) The general experimental platform adopts multi-stage protection, including direct current side protection, alternating current side protection and full-bridge submodule protection, each stage of protection comprises hardware and software protection, and the safety and reliability of the experimental process are ensured.

(4) The sampling module adopted by the invention comprises converter level sampling and full-bridge submodule sampling, the obtained experimental data is more comprehensive, and the required data can be selected according to experimental requirements.

Drawings

FIG. 1 is a schematic diagram of a modular multifunctional MMC topology universal experimental platform according to the present invention;

FIG. 2 is a block diagram of a modular multifunctional MMC topology universal experimental platform according to the present invention;

FIG. 3 is a full bridge block diagram;

FIG. 4 is a diagram of a full bridge sub-module configuration;

fig. 5 is a diagram of a converter level sampling architecture;

FIG. 6 is a block diagram of a master controller;

FIG. 7 is a block diagram of an inductance module;

FIG. 8 is a schematic diagram of the MMC;

FIG. 9 is a schematic block diagram of the HMMC concept;

FIG. 10 is a schematic view of the AAMC principle;

FIG. 11 is a schematic block diagram of HCMC;

fig. 12 is a schematic block diagram of a modular multilevel DC-DC converter;

fig. 13 is a schematic diagram of connection of each module when the general experimental platform performs MMC, HMMC, AAMC experiment;

FIG. 14 is a schematic diagram showing the connection of the modules of the HCMC experiment performed by the universal experiment platform;

fig. 15 is a schematic diagram of the connection of the modules of the universal experimental platform when the modular multilevel DC-DC experiment is performed.

Detailed Description

In order to more particularly describe the present invention, the following detailed description of the technical scheme of the present invention is provided with reference to the accompanying drawings and the specific embodiments.

1-2, a modular multifunctional MMC topology universal experimental platform is composed of a cabinet and modular hardware installed in the cabinet. The direct-current side voltage is 800V adjustable, the effective value of the alternating-current side phase voltage is 220V adjustable, and the total power reaches 10KVA.

The modularized hardware comprises a bridge arm module, a sampling module, a power module, a control module, an inductance module, an isolation transformer and a protection module, which can be expanded according to requirements.

The bridge arm modules are three groups, and each group of bridge arm modules respectively represents A, B, C three phases, and each group of bridge arm modules comprises an upper bridge arm module and a lower bridge arm module, and the total number of the bridge arm modules is 6. The input end of each phase of upper bridge arm module is connected with the positive pole of the direct current side power port of the power module after being subjected to direct current side protection of the converter level current sampling and protecting module of the sampling module, the input end of the lower bridge arm module is connected with the negative pole of the direct current side power port of the power module, the output ends of the upper bridge arm module and the lower bridge arm module are connected with the input end of the inductance module after being subjected to converter level current sampling of the sampling module, the two output ends of each phase of the inductance module are connected with each other, and are connected with the input end of the isolation transformer after being subjected to alternating current side protection of the converter level current sampling and protecting module of the sampling module, and the output end of the isolation transformer is connected with the alternating current side power port of the power module.

The sampling module is provided with multiple voltage and current detection ports, wherein the voltage detection ports are connected in parallel with the upper bridge arm module, the lower bridge arm module, the input end and the output end of the isolation transformer and the direct current side power supply port of the power supply module.

And a plurality of display screens are arranged in the cabinet. One part of the bridge arm modules are connected with the main controller through network cables, and the bridge arm modules can display states including a normal state, an operating state, an overvoltage state, an overcurrent state, an overtemperature state and communication errors; the other part is connected with the power supply module and the sampling module, and can display the voltage and current of each node of the converter. The display screen can help experimenters to quickly and accurately know various data and state information, accurately locate fault points when faults occur conveniently, and quickly determine fault reasons.

The bridge arm modules are formed by connecting a plurality of full-bridge sub-modules in series, each full-bridge sub-module is an independent individual with complete functions, and in one specific implementation of the invention, as shown in fig. 2, each bridge arm is provided with 6 full-bridge sub-modules, the total number of which is 36, and the expansion can be realized; the Quan Qiaozi module uses IGBT as the full-control power device. The full-bridge submodule structure is shown in fig. 4, is formed by full-bridge submodule sampling of a sampling module, full-bridge submodule protection of a slave controller, a power board and a protection module, and cools the IGBT module through a cooling fan. The front surface of the device is provided with a status indicator lamp which can display fault type and running status information, and the back surface of the device comprises a power interface and an optical fiber interface. In one embodiment of the invention, the full-bridge sub-module is installed by adopting a drawer type chassis structure, and one drawer type chassis comprises 3 sub-modules which are A, B, C three phases respectively, so that the expansion is convenient.

The Quan Qiaozi module can be controlled to be converted into a shaping circuit formed by the Quan Qiaozi module or the half-bridge submodule, and can also be controlled to be converted into a conductive switch circuit. As shown in fig. 3, when T1 and T4, T2 and T3 are complementarily and alternately turned on, the submodule is converted into a shaping circuit composed of a full-bridge submodule; when T3 is opened, T4 is closed, and T1 and T2 are complementarily conducted, the submodule is converted into a shaping circuit formed by the half-bridge submodule; when T2 and T4 are disconnected, T1 and T3 are simultaneously turned on and off, or T1 and T3 are turned off, and T2 and T4 are simultaneously turned on and off, the submodule is turned into an on switch circuit.

The sampling module is divided into converter level sampling and full-bridge submodule sampling, and the structure of the converter level sampling is shown in fig. 5 and comprises converter level voltage and current sampling. The converter level sampling is an independent unit with complete functions, and is composed of a sampling plate and a slave controller, 14 paths of voltage signals and 7 paths of current signals can be provided for sampling, and the reverse side comprises a power interface and an optical fiber interface. In one embodiment of the invention, the sampling module is installed by a drawer type chassis, and one drawer type chassis comprises 2 sampling modules, so that the expansion is convenient.

The power module comprises an auxiliary power module, an alternating current side power port and a direct current side power port. The alternating current side power supply port and the direct current side power supply port can be connected with an independent alternating current/direct current source or a plurality of universal experiment platforms or other types of converters, so that multi-terminal cooperative control experiments can be conveniently carried out.

The control module comprises a master controller and a slave controller. The structure of the master controller is shown in fig. 6, which is PE-Expert4 of Myway company, integrates DSP, FPGA and a plurality of optical fiber communication interfaces, and communicates with each slave controller through optical fibers, thereby being convenient for expansion. The slave controller integrates the high-performance DSP and the optical fiber communication interface, and is small and convenient.

The control module is internally integrated with modularized software, comprises basic control and debugging algorithms suitable for MMC, HMMC, AAMC, HCMH and modularized multi-level DC-DC converters, and can insert new control and modulation algorithms into corresponding positions of corresponding algorithms of the modularized software according to scientific research requirements. In the one-time power-on experiment process, the universal experiment platform can be directly switched among a plurality of experiment modes through software commands.

The inductance module structure is shown in fig. 7, and is composed of 6 groups of inductance submodules, namely AP, AN, BP, BN, CP, CN, each group is composed of 4 inductances with the same inductance value, 4 different inductance values are realized through different serial connection modes, namely 3.2mH, 6.4mH, 9.6mH and 12.8mH, and when more inductance values or larger inductance values are needed, the inductance coils can be replaced or the inductance modules can be directly connected in series. In one embodiment of the invention, the inductance module is of drawer type design, which is convenient for expansion.

The protection module comprises direct current side protection, alternating current side protection and full-bridge submodule protection, and both the protection module comprises hardware protection and software protection. The hardware parts of direct current side protection and alternating current side protection all include series connection's air switch and controllable circuit breaker, and wherein, a controllable circuit breaker links to each other with a snubber resistor as shown in fig. 1, mainly uses when full-bridge submodule piece electric capacity charges, and another controllable circuit breaker is parallelly connected with snubber resistor and controllable circuit breaker, takes charge of cutting off snubber resistor when charging is accomplished. The protection module of the invention realizes multistage protection in the experimental process.

Further, the modular multifunctional MMC topology universal experimental platform provided by the invention comprises the following experimental steps:

step 1: and determining the topology type, the shaping circuit and the number of the conducting switch circuits according to experimental requirements. The shaping circuit and the conduction switch circuit are realized as follows:

for the shaping circuit, it can operate in full-bridge and half-bridge configuration states, the full-bridge configuration is shown in fig. 3. When the shaping circuit operates in a full-bridge structure, the T1 and the T4 are controlled to be conducted, the T2 and the T3 are controlled to be turned off, and then a positive level is output and is expressed as a put-in state; the control T1 and the control T4 are turned off, and the control T2 and the control T3 are turned on, so that negative level is output and the control is expressed as a put-in state; and controlling the T1 and the T3 to be conducted, the T2 and the T4 to be turned off, or the T1 and the T3 to be turned off, and the T2 and the T4 to be conducted, outputting a zero level and representing a cutting state. When the shaping circuit operates in a half-bridge structure, the normally-closed T4 of the T3 is controlled to be normally-closed, and the T1 and the T2 are alternately conducted to realize capacitor switching.

For the on-switch circuit, the T1 and the T3 are controlled to be on, the T2 and the T4 are controlled to be off, or the T1 and the T3 are controlled to be off, and the T2 and the T4 are controlled to be on, so that the switching function of the full-bridge submodule can be realized.

And adjusting the number of the full-bridge submodules loaded and operated according to the number requirements of the shaping circuit and the on-switch circuit. If the number of the full-bridge submodules required for operation is smaller than the number provided by the universal experiment platform, controlling redundant full-bridge submodules to be in a cutting state through modularized software; if the number of the full-bridge submodules required for operation is equal to the number provided by the universal experiment platform, the modularized software does not need to be adjusted; if the number of the full-bridge submodules required for operation is larger than the number provided by the universal experiment platform, a plurality of additional full-bridge submodules are added in series.

Step 2: and selecting a corresponding connection mode, control and modulation algorithm according to the topology type. The method specifically comprises the following steps:

scheme 1: MMC experiment

The schematic block diagram of the MMC is shown in fig. 8, and according to the experimental requirement, the MMC control and debugging algorithm is written in the corresponding position of the modularized software, and since the bridge arm modules of the MMC topology are formed by connecting the shaping circuits formed by the full-bridge submodules in series, the non-conductive switch circuit is correspondingly presented to the general experimental platform, as shown in fig. 13. Taking one phase as an example, 6 full-bridge submodules of an upper bridge arm and a lower bridge arm are connected in series, the direct current side of the full-bridge submodules is connected to a direct current bus, one ends of the upper bridge arm and the lower bridge arm, which are close to the alternating current side, pass through the bus, are sampled by a converter stage and are combined into an alternating current bus after being subjected to inductance module, and enter an isolation transformer. At this time, the Quan Qiaozi modules are all controlled to be shaping circuits, and can all run in a full-bridge or half-bridge structure state, so that experiments can be performed.

Scheme 2: HMMC experiment

The schematic structure diagram of HMMC is shown in fig. 9, and HMMC control and debugging algorithm is written in the corresponding position of the modularized software according to the experiment requirement, and because the bridge arm modules of HMMC topology are formed by serially connecting shaping circuits, the full-bridge structure and the half-bridge structure exist simultaneously, and no switch circuit is conducted, so that the proposed general experiment platform is correspondingly embodied as shown in fig. 13. Taking one phase as an example, on the connection of hardware, the HMMC is the same as the MMC; the difference is that the full-bridge submodule is controlled to be in a full-bridge or half-bridge structure state according to the number of the required full-bridge and half-bridge structures, so that experiments can be carried out.

Scheme 3: AAMC experiment

The principle structure diagram of the AAMC is shown in fig. 10, and according to the experimental requirement, an AAMC control and debugging algorithm is written in the corresponding position of the modularized software, and as the bridge arm module of the AAMC topology is formed by connecting a shaping circuit and a conducting switch circuit in series, the shaping circuit can be in a full-bridge or half-bridge structure, and the shaping circuit is correspondingly embodied in the proposed general experimental platform as shown in fig. 13. Taking one phase as an example, in the connection of hardware, AAMC is the same as MMC and HMMC; the difference is that the full-bridge submodule is controlled to be in a state of conducting the switch circuit, the full-bridge or the half-bridge structure according to the number of the needed conducting switch circuit, the full-bridge and the half-bridge structure, so that experiments can be carried out.

Scheme 4: HCMC experiment

The principle structure diagram of the HCMC is shown in fig. 11, and according to the experimental requirement, the HCMC control and debugging algorithm is written in the corresponding position of the modularized software, and because the bridge arm module of the HCMC topology is composed of a shaping circuit and a conducting switch circuit, the shaping circuit is positioned at the ac output side, and is connected in series, the conducting switch circuit is positioned at the upper and lower bridge arms, and is connected in series, the proposed general experimental platform is correspondingly shown in fig. 14. Taking one phase as an example, on the connection of hardware, the connection mode of the full-bridge submodule needs to be finely adjusted, namely: the full-bridge submodules serving as the conducting switch circuits are kept in series, the full-bridge submodules serving as the shaping circuits are also kept in series, the conducting switch circuits of the upper bridge arm and the lower bridge arm are required to be connected and converged, the conducting switch circuits are connected with an input port of the shaping circuits, the other end of the shaping circuits is used as an output end to be connected with an input end of the inductance module, and other connection modes are unchanged. At this time, the full-bridge submodule is controlled to be in a state of conducting the switch circuit or the full-bridge structure according to the quantity of the needed conducting switch circuit and the full-bridge structure, so that experiments can be carried out.

Scheme 5: modular multilevel DC-DC converter experiment

The principle structural diagram of the modularized multi-level DC-DC converter is shown in fig. 12, a control and debugging algorithm of the modularized multi-level DC-DC converter is written in a corresponding position of modularized software according to experimental requirements, a main circuit of the modularized multi-level DC-DC converter with single-ended output only needs an upper bridge arm module and a lower bridge arm module, and an output resonance circuit can be composed of an inductance module and another bridge arm module. The corresponding proposed generic experimental platform is embodied as shown in fig. 15. On the connection of hardware, an output port of a bridge arm where the main circuit is positioned is connected with an output port of another bridge arm module through an inductance module. In control, the upper bridge arm module and the lower bridge arm module of the main circuit control the full-bridge submodule to be in a full-bridge or half-bridge structure state according to the number of required full-bridge or half-bridge structures, the bridge arm module of the output resonant circuit is used as an adjustable capacitor, the overall capacitance value of the bridge arm module is adjusted by controlling the switching number of the full-bridge submodule, and charging is not needed during operation. The full-bridge submodules IGBT of the rest bridge arm modules are in an off state without applying any signals, and the experiment can be performed.

Step 3: and starting the power module, writing corresponding modularized software into the main controller, running, and detecting corresponding data.

In summary, the modular multifunctional MMC topology universal experimental platform provided by the invention utilizes modular hardware and corresponding modular software, not only can meet various MMC topology experiments, but also can interconnect various experimental platforms through ports reserved on an alternating current side and a direct current side, so as to achieve the aim of multi-terminal cooperative control. The universal experimental platform has the advantages of small occupied area, convenient and fast switching among topologies, high safety and reliability, strong flexibility and expansibility and the like, and is beneficial to accelerating the conversion of scientific research results.

The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those having ordinary skill in the art that various modifications to the above-described embodiments may be readily made and the generic principles described herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications within the scope of the present invention.

Claims (5)

1. The modularized multifunctional MMC topology universal experimental platform is characterized by being capable of providing a universal experimental platform for various MMC converter level topologies; the experimental platform consists of a cabinet and modularized hardware installed in the cabinet, wherein the modularized hardware comprises a bridge arm module, a sampling module, a power supply module, a control module, an inductance module, an isolation transformer and a protection module; the working states of the sampling module, the protection module, the bridge arm module, the power supply module, the inductance module and the isolation transformer are controlled by the control module;

the multiple MMC converter level topologies comprise an AAMC topology, an HCMC topology and a modularized multi-level DC-DC topology; the sampling module is divided into converter level sampling and full-bridge submodule sampling, each sampling module comprises a sampling plate and a slave controller, and is provided with multiple paths of voltage detection ports and current detection ports, wherein the voltage detection ports are arranged at the positions of an upper bridge arm module, a lower bridge arm module, an input end and an output end of an isolation transformer and a direct current side power supply port of a power supply module in parallel, and the current detection ports are arranged at the bridge arm side, an alternating current side and a direct current side of the converter;

the protection module comprises a direct current side protection, an alternating current side protection and a full-bridge submodule protection, wherein the direct current side protection and the alternating current side protection comprise an air switch and a controllable circuit breaker which are connected in series;

the bridge arm module comprises an upper bridge arm module and a lower bridge arm module, wherein the upper bridge arm module and the lower bridge arm module are formed by connecting a plurality of full-bridge submodules in series, and can be converted into a conduction switch circuit and a shaping circuit after being controlled by the control module; each full-bridge submodule is an independent unit consisting of full-bridge submodule sampling, a slave controller, a power board and full-bridge submodule protection; the input end of each phase upper bridge arm module is connected with the positive electrode of the direct current side power port of the power module after being subjected to direct current sampling of the converter level of the sampling module and the direct current side protection of the protection module; the input end of the lower bridge arm module is connected with the negative electrode of the direct-current side power port of the power module; the output ends of the upper bridge arm module and the lower bridge arm module are connected with the input end of the inductance module after being sampled by the converter level of the sampling module; two output ends of each phase in the inductance module are connected, and are connected with the input end of the isolation transformer after being sampled by the converter level of the sampling module and being protected by the alternating current side of the protection module; the output end of the isolation transformer is connected with an alternating current side power port of the power module;

the control module comprises a master controller and slave controllers, wherein the master controller is provided with a plurality of optical fiber communication interfaces, and the optical fiber communication interfaces are communicated with the slave controllers through optical fibers; the slave controller is integrated with a high-performance DSP;

the AAMC topology is realized by controlling a bridge arm module through an AAMC control and debugging program in a control module, so that part of full-bridge submodules are converted into a switch-on circuit, capacitors in the AAMC topology are cut off, and current circulation is ensured; the other part of the full-bridge submodule is converted into a shaping circuit;

the HCMC topology is realized by controlling a bridge arm module through a control and debugging program of the HCMC in the control module, so that part of full-bridge submodules are converted into a switch-on circuit, and the capacitor in the HCMC topology is cut off and the circulation of current is ensured; the other part of the full-bridge submodule is converted into a shaping circuit; meanwhile, the conducting switch circuits in the upper bridge arm module and the lower bridge arm module are controlled to be connected to an output port, and are connected with an input port of a shaping circuit, and the output port of the shaping circuit is connected with the input end of the inductance module; then, according to the quantity of the required on-switch circuits and the full-bridge structures, the full-bridge submodules are controlled to be in a state of the on-switch circuits or the full-bridge structures;

the modularized multi-level DC-DC topology is realized by controlling bridge arm modules through modularized multi-level DC-DC control and debugging programs in the control modules; for a modularized multi-level DC-DC converter with single-ended output, a main circuit only selects a pair of upper bridge arm modules and lower bridge arm modules, an output resonance circuit consists of an inductance module and another bridge arm module, and an output port of the bridge arm where the main circuit is positioned is connected with an output port of the other bridge arm module through the inductance module; the upper bridge arm module and the lower bridge arm module of the main circuit control the full-bridge submodule to be in a full-bridge structure or half-bridge structure state according to the number of required full-bridge structures or half-bridge structures, the bridge arm module of the output resonant circuit is used as an adjustable capacitor, the overall capacitance value of the bridge arm module is adjusted by controlling the switching number of the full-bridge submodule, and charging is not needed during operation.

2. The modular multifunctional MMC topology universal experimental platform according to claim 1, wherein a bridge arm module state display screen and a voltage and current display screen are arranged in the cabinet, the bridge arm module state display screen is connected with the main controller through a network cable, and displayable bridge arm module states comprise a normal state, an operating state, an overvoltage state, an overcurrent state, an overtemperature state and a communication error; the voltage and current display screen is connected with the power module and the sampling module.

3. The modular multi-functional MMC-like topology universal experimental platform of claim 1, wherein the power module comprises an auxiliary power module, an ac-side power port, and a dc-side power port.

4. The modular multifunctional MMC topology universal experimental platform of claim 1, wherein said inductance modules are comprised of 6 groups of inductance submodules with adjustable inductance values.

5. An experimental method of the modular multifunctional MMC-type topology universal experimental platform as recited in claim 1, comprising the steps of:

step 1: determining topology types and the number of full-bridge submodules required by a shaping circuit and a switching-on circuit according to experimental requirements, and controlling redundant full-bridge submodules to be in a cut-off state if the required number is smaller than the number provided by a general experimental platform; if the number is equal to the number provided by the universal experiment platform, no adjustment is needed; if the number is larger than the number provided by the universal experiment platform, a plurality of additional full-bridge submodules are added in series;

step 2: a modularized program is integrated in a control module of the test platform, and comprises control and debugging programs of AAMC, HCMH and modularized multi-level DC-DC converter, and corresponding connection modes and control and modulation programs are selected according to topology types;

step 3: and starting the power module, executing corresponding control and debugging programs through the main controller, acquiring experimental data and storing the experimental data.